Abstract: In this paper, A barrier function descent direction method for implementing CDMA multi-user detection (BMD) is proposed. As compared to conventional detectors and neural network optimal algorithms, the method derives a new descent direction from the barrier function other than the gradient direction. Numerical results show that the method is always able to find the global minimization point. It has many advantages featuring near-far effect resistance, able to suppressing multiple access interference and channel noise, etc. The method paves a new way for realizing optimal multi-user detection in CDMA system.